EloPhos® is a system for the recovery of phosphate from digested sewage sludge emanating from wastewater treatment plants with biological phosphate (bio-p) removal in the form of magnesium-ammonium-phosphate ('map' or 'struvite') fertiliser.
EloPhos® is a proprietary technology of ELIQUO STULZ (patent pending).
The EloPhos® process is based on the precipitation of dissolved phosphate from digested sewage sludge using magnesium salts, usually magnesium chloride (mgcl2). Crystals which are grown in the EloPhos® crystallisation reactor up to approximately 1-2mm diameter or above can subsequently be separated from the sludge.
Phosphorus is one of the raw materials expected to be subject to severe shortages in the near future. Whereas in 1979 the global stocks were estimated to be sufficient for 500 years at the forecast rate of consumption, in 2012 the amount of exploitable stocks was estimated to be sufficient for only around 100 years. The majority of raw phosphate extracted today is used for the production of fertilisers.
Wastewater has the potential to be a significant source of secondary phosphate. Historically, phosphorus recovery from wastewater was achieved by land application of sewage sludge. However, with the increasing use of thermal sludge disintegration processes where phosphorus is released, technical solutions for phosphorus recovery from the sludge liquid are of growing importance.
- An increase of up to approx 5% in solids content in the digested and dewatered sewage sludge = reduced sludge disposal costs
- A reduction of up to approx 20% in the consumption of polymer for the dewatering of the digested sludge = reduced sludge dewatering costs
- A reduction in crystallisation problems by virtue of unwanted, spontaneous MAP deposits in the zone downstream from the EloPhos® system, eg in the digested sludge dewatering zone = reduced maintenance costs
- A reduction of up to approx 95% in phosphate recycle load / sludge liquor = reduced operational costs
- The recovery of MAP fertiliser = revenues
Increasingly, both thermal hydrolysis processes (THP) and bio-P are found together. For such plants, the EloPhos® system is an ideal addition as it removes the phosphorus which is released by the THP process. EloPhos® is therefore also an ideal partner to ELIQUO’s LysoTherm® system (thermal sludge hydrolysis process) in such circumstances.